For a heat pump, the second law ofefficiency can be written in the form ............

A

(First law efficiency) $$\times \left(1 - \frac{T_a}{T_o}\right)$$

B

(First law efficiency) $$\times \left(1 + \frac{T_o}{T_a}\right)$$

C

(First law efficiency) $$\times \left(1 - \frac{T_o}{T_a}\right)$$

D

(First law efficiency) $$\times \left(1 + \frac{T_a}{T_o}\right)$$